Use tables of standard heats of formation to determine the enthalpy change of each of the following reactions:

a$)$ Ag$2$O$($s$)+$ H$2($g$)2$Ag$($s$)+$ H$2$O$($l$)$

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b$)$ Fe$2$O$3($s$)+3$CO$($g$)2$Fe$($s$)+3$CO$2($g$)$

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c$)2$Ag$1+($aq$)+$ Pb$($s$)2$Ag$($s$)+$ Pb$2+($aq$)$

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d$)4$NH$3($g$)+5$O$2($g$)4$NO$($g$)+6$H$2$O$($g$)$

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e$)$ CH$3$COOH$($l$)+2$O$2($g$)2$CO$2($g$)+2$H$2$O$($l$)$

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How do find the values for standard enthalpies not on the standard table?